The present invention is directed to certain trifluoroalkene compounds. Of particular interest are compounds of the formula RCF.sub.3 where R is a C.sub.4 to C.sub.7 unsaturated alkyl radical. The invention is also particularly directed to the preparation of such compounds in high selectivity by an addition reaction of lower (C.sub.3 or C.sub.4) trifluoroalkenes with lower olefins.
Fluorinated hydrocarbons such as those of this invention are known to have utility as refrigerants, pesticides, dielectric fluids, heat transfer fluids, solvents, and intermediates in various chemical reactions, including polymerization.
Methods are known in the art for the preparation of a variety of fluorocarbons (compounds containing only carbon and fluorine atoms) and partially-fluorinated hydrocarbons (compounds containing carbon, hydrogen and fluorine atoms), the latter group specifically including the one trifluoroalkene compound 3,3,3-trifluoropropene.
According to U.S. Pat. Nos. 3,062,901 and 3,067,263 and prior art cited therein, at least five different approaches have been proposed for the preparation of 3,3,3-trifluoropropene. U.S. Pat. No. 3,062,901 discloses and claims a process in which ethane is contacted at a temperature from about 250.degree. to 700.degree. C. with a compound of the formula CF.sub.3 X wherein X is chlorine or bromine. U.S. Pat. No. 3,067,263 describes and claims a similar process for the contact of ethylene with CF.sub.3 X at a temperature from about 600.degree. to 1000.degree. C. This process is shown to have a low yield of the desired trifluoropropylene, with the principal product of the reaction being the side product CF.sub.3 H. These two patents also teach that 3,3,3-trifluoropropene can be prepared in a multistep process including steps for converting ethyl trifluoroacetate to trifluoroacetone, reducing the trifluoroacetone to the alcohol, and dehydrating the alcohol to 3,3,3-trifluoropropene. Another method disclosed in these patents involves the free radical addition of CF.sub.3 I to ethylene in the presence of a catalyst followed by dehydroiodination. Still another method described involves reacting CCl.sub.4 with HBr in the presence of a catalyst to product CCl.sub.3 --CH.sub.2 --CH.sub.2 Br and reacting this intermediate with hydrogen fluoride.
Insofar as is known, it has not been suggested that either such methods can be extended to the preparation of the higher trifluoroalkene compounds as are of interest in the present invention.
Other prior art generally relevant to aspects of this invention pertaining to fluorinated hydrocarbons and their preparation, includes the disclosure in U.S. Pat. No. 3,456,025 of the preparation of gem-difluoroalkenes (1,1-difluoroalkenes) by dehydrofluorination of trifluoroalkanes in the presence of a fluorided alumina catalyst at a temperature in the range from 500.degree. to 1200.degree. C. U.S. Pat. No. 2,551,639 teaches methods for the condensation of 2-olefins with polyhalogenated alkanes to produce mixtures of different unsaturated halogenated compounds. U.S. Pat. No. 2,709,183 describes the direct reaction of hydrogen fluoride with carbon compounds at high temperature (i.e., at least 2500.degree. C.). U.S. Pat. Nos. 2,637,747, 2,767,227, and 3,904,701 teach different methods for the preparation of trifluoroethane and related compounds. U.S. Pat. No. 3,755,477 is directed to a gas-phase reaction of hydrogen fluoride with halogenated alkanes or halogenated alkenes in the presence of a chromium oxide catalyst.
In one important aspect, the invention centers upon the use of certain palladium catalysts to promote the reaction between an olefin reactant and a trifluoroalkene reactant. As described in U.S. Pat. No. 4,436,946 and other prior art cited therein, palladium compounds are known in the art to catalyze the conversion of lower olefins to their dimers and other oligomerizers.